<!DOCTYPE html>
<html>
<head>
 <style>
     .father{
         border: 1px solid black;
         overflow: scroll;/*让副元素认出子元素*/
     }
    .a,.b,.c{
    width: 200px;
    height: 200px;
    margin: 10px;/*内边框*/
    border: 1px solid black;/*边框*/
    float: left;
 }
 .c{
     z-index: 3;
     overflow:auto;/*滚动条*/
     position:fixed;
     top: 100px;
     background-color: aqua
     
     
 }
 .a{
     z-index: 2;
     position: relative;
     background-color: yellow
     
 }
 .d{
     width: 1500px;
     height: 1000px;
     border: 1px solid black;/*边框*/
     background: url(E:\\张峰华\\网页设计\\3.25盒子模型\\1.jpg);
 }
.b{
    position: relative;
    top: 150px;
    background-color: pink;
    right:  222px;
    z-index: 4;   
}
 </style>
</head>
<body>
    <div class="father">
    <div class="a"></div>
    <div class="b"></div>
    <div class="c">
    </div>
    <div class="d"></div> 
</body>
</html>